In a known cable of this kind, as for example disclosed in German Pat. No. 33 05 246, the core of the cable is formed by an insulating layer of flat rectangular cross-section, in the interior of which the conductors of the cable are so arranged in immediate proximity of the one flat side of the core that they extend in longitudinal direction of the cable one parallel to the other in about one plane. Spaced apart recesses extend from the other flat side of the cable core into the insulating layer. In these recesses electronic circuit units are arranged, the recesses having dimensions which are appreciably greater than the dimensions of the electronic circuit units. The gaps between each of the electronic circuit units and the respective recess surrounding it are filled out with a permanently elastic, electrically insulating mass for protection against polution and moisture. The thus formed core of the known cable is surrounded by a multi-layer sheath which comprises a wrapped around tape with components swelling up on access of water, a layer of a material having a high electrical conductivity and a layer of a plastomeric or elastomeric synthetic material which is to protect the inner parts of the cable against chemical influences coming from outside.
The structure of this known cable can lead to serious disadvantages, since a sheath made up of wound tapes and an outer synthetic material layer in the case of a direct laying of the cable in the soil does not afford adequate protection against moisture, other chemical influences and especially against electrical and magnetic disturbing influences as they are for example caused by lightning strikes in the direct proximity of the cable.
Therefore it is an objective of the invention to provide a cable of the initially named kind that possesses a simple structure, is favourable in costs and even under extreme conditions of use assures an excellent protection of the circuit units integrated into the cable against environmental influences of all kinds.